## Alkali vs Acid Chemical Injuries **Key Point:** Alkali (base) injuries are more destructive than acid injuries because they cause liquefactive necrosis and penetrate deeper into ocular tissues. ### Mechanism of Damage **High-Yield:** Sodium hydroxide (NaOH) and other strong alkalis: - Cause liquefactive necrosis of proteins - Saponify lipids in cell membranes - Penetrate corneal stroma and anterior chamber - Cause progressive damage even after initial exposure - Lead to corneal opacification, anterior synechiae, and vision loss ### Comparison Table: Acid vs Alkali Injuries | Feature | Acid Injuries | Alkali Injuries | | --- | --- | --- | | Type of necrosis | Coagulative | Liquefactive | | Corneal penetration | Superficial (self-limited) | Deep (progressive) | | Severity | Moderate | Severe | | Anterior chamber involvement | Rare | Common | | Long-term complications | Less common | Frequent (symblepharon, pannus) | | Prognosis | Better | Worse | **Clinical Pearl:** Acid injuries form a protein precipitate (coagulum) that acts as a barrier, limiting further penetration. Alkali injuries have no such protective barrier and continue to cause damage for hours to days. **Mnemonic:** **ALKALI = Aggressive, Liquefactive, Keeps penetrating, Awful prognosis, Liquefies membranes, Immediate and delayed damage** ### Why Sodium Hydroxide is Most Severe - Highest pH (14) among common alkalis - Rapid saponification of lipids - Penetrates Descemet's membrane - Causes anterior uveitis, iridocyclitis, and secondary glaucoma - Progressive corneal scarring and vascularization [cite:Parson's Diseases of the Eye 22e Ch 8] 
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